[2] While the House and Cloverleaf revolvers were chambered in the .41 caliber, relatively well known at the time, William Mason, the engineer working on the design of the Open Top, chose the more powerful .44 Henry cartridge.

Mason brought some innovations to his gun: apart from the breech-loading cylinder, he designed unique frame, cylinder and barrel for the first Colt revolver with non-interchangeable parts with the older percussion pistols and moved the rear sight to the rear of the barrel as opposed to the hammer or the breechblock of the earlier efforts.

This new design started production in 1873, giving birth to a new model, the Colt Single Action Army, and a new serial numbering.

The "Two July" patents were also found on very early Colt Single Action Army revolvers.

[2] Cimarron Firearms of Fredericksburg, Texas, imports a replica of the Open-Top revolver that is based on an antique Open Top that the company sent to Uberti to reverse-engineer.